From: adam@address.invalid   
      
   unruh wrote:   
   > On 2012-11-16, Adam  wrote:   
   >>    Note -c is used twice for a read/write test.  With -v, it will keep   
   >> you informed of its progress.  Over 30 hours sounds quite within reason   
   >> for a ~1 TB partition.   
   >   
   > Write 1TB of data at 100MB/s say is about 3 hours. Ie, it should not be   
   > taking 30 hours. (reading should be a bit faster, and the comparison   
   > should be instantaneous) Unless the mke2fs is writing one byte, then   
   > reading it back and comparing it (which would be lunacy)   
      
   Except I believe this is a USB 2.0 external drive, and my experience is   
   that real-world transfer speed for USB 2.0 is about 20 MB/s, not its   
   theoretical maximum of 60 MB/s.  Also IIRC the r/w test of 'mke2fs' is   
   four passes (55, AA, 00, FF).   
      
   If, as you say, at 100 MB/s writing 1 TB is about three hours and   
   reading is similar, that's six hours per pass at 100 MB/s or five times   
   that at 20 MB/s.  Multiply by four passes and that's 120 hours!  Now   
   that figure is way too high, but it gives some idea why "mke2fs -cc"   
   takes so long.   
      
   Back when I was shopping for an external USB 2.0 1 TB drive in early   
   2009, a lot of the reviews mentioned taking well over a day to reformat   
   it into NTFS or Mac HFS/HFS+.  On my system, I recall 'tune2fs'   
   reporting a transfer rate of about 20 MB/s, compared to about 60 MB/s   
   for the (ca. 2007) internal HD.  Fortunately the model I bought also had   
   an eSATA connection, and using that it was even faster than the internal HD.   
      
   Adam   
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